This is Kira's artwork collection for most all PS2 games, optimized for use with Open PS2 Loader (OPL). This was originally shared as an ISO and was hosted on MediaFire, but as MediaFire links can be volatile and disappear overnight, and to help preserve the hard work put into this, I am uploading a backup archive here.
The entire pack is as-is, with no changes made from Kira's original work other than repacking it as an lzma2-compressed 7zip archive for multi-core
unpacking benefits, and make it easier to access the files.
The pack contains almost 61,000 images. If you are using OPL through SMB, you can just unpack this set, place it next to your DVD and CD folders and ensure it is called ART and you're good to go. If you use a FAT-formatted hard drive you won't be able to unpack everything due to its file count limitations, so in that case you'll have to pick and choose which images you would like to copy over.
This is the recent-most 02/26/20 release of Kira's pack as of the time of this upload. The original PSX-place thread can be found right here. All credit goes to Kira for their hard working putting all this together, so please be sure to thank them for their fantastic work.